Show ALL the icons in demo.py and adjust the show-icon.py help.

- demo.py was showing only 32
- show-icon.py's help said there were 42
- My tests show there to be 43 (#43 being "night-time thunderstorms")
- My tests indicate that requesting icons up to 48 doesn't cause problems
  so I'll let it do that because it makes things less confusing.
  (And it's possible some devices might actually have icons in slots 44-48)